New XS_SET_TARGET

Stubdomains (and probably other domain disagregation elements too)
need to be able to tinker with another domain.  This adds
XS_SET_TARGET so that XenStore allows domains to have permissions on
files on which the "target" has permissions.  This also adds
xs_set_target, called by the domain builder when the 'target' option
is used in the configuration.

Signed-off-by: Samuel Thibault <samuel.thibault@eu.citrix.com>

tools/python/xen/lowlevel/xs/xs.c

@@ -619,6 +619,36 @@ static PyObject *xspy_introduce_domain(XsHandle *self, PyObject *args)
     return none(result);
 }
 
+#define xspy_set_target_doc "\n"					\
+        "Tell xenstore that a domain is targetting another one so it\n" \
+        "should let it tinker with it.\n"	                        \
+	" dom    [int]   : domain id\n"					\
+	" target [int]   : domain id of the target\n"			\
+	"\n"								\
+	"Returns None on success.\n"					\
+	"Raises xen.lowlevel.xs.Error on error.\n"			\
+	"\n"
+
+static PyObject *xspy_set_target(XsHandle *self, PyObject *args)
+{
+    uint32_t dom;
+    uint32_t target;
+
+    struct xs_handle *xh = xshandle(self);
+    bool result = 0;
+
+    if (!xh)
+        return NULL;
+    if (!PyArg_ParseTuple(args, "ii", &dom, &target))
+        return NULL;
+
+    Py_BEGIN_ALLOW_THREADS
+    result = xs_set_target(xh, dom, target);
+    Py_END_ALLOW_THREADS
+
+    return none(result);
+}
+
 #define xspy_resume_domain_doc "\n"                                \
 	"Tell xenstore to clear its shutdown flag for a domain.\n" \
 	"This ensures that a subsequent shutdown will fire the\n"  \
@@ -817,6 +847,7 @@ static PyMethodDef xshandle_methods[] = {
     XSPY_METH(transaction_start, METH_NOARGS),
     XSPY_METH(transaction_end,   METH_VARARGS | METH_KEYWORDS),
     XSPY_METH(introduce_domain,  METH_VARARGS),
+    XSPY_METH(set_target,        METH_VARARGS),
     XSPY_METH(resume_domain,     METH_VARARGS),
     XSPY_METH(release_domain,    METH_VARARGS),
     XSPY_METH(close,             METH_NOARGS),

tools/python/xen/xend/XendDomainInfo.py

@@ -47,7 +47,7 @@ from xen.xend.XendError import XendError, VmError
 from xen.xend.XendDevices import XendDevices
 from xen.xend.XendTask import XendTask
 from xen.xend.xenstore.xstransact import xstransact, complete
-from xen.xend.xenstore.xsutil import GetDomainPath, IntroduceDomain, ResumeDomain
+from xen.xend.xenstore.xsutil import GetDomainPath, IntroduceDomain, SetTarget, ResumeDomain
 from xen.xend.xenstore.xswatch import xswatch
 from xen.xend.XendConstants import *
 from xen.xend.XendAPIConstants import *
@@ -883,6 +883,9 @@ class XendDomainInfo:
     def storeVm(self, *args):
         return xstransact.Store(self.vmpath, *args)
 
+    def permissionsVm(self, *args):
+        return xstransact.SetPermissions(self.vmpath, *args)
+
 
     def _readVmTxn(self, transaction,  *args):
         paths = map(lambda x: self.vmpath + "/" + x, args)
@@ -904,6 +907,10 @@ class XendDomainInfo:
         paths = map(lambda x: self.vmpath + "/" + x, args)
         return transaction.store(*paths)
 
+    def permissionsVmTxn(self, transaction,  *args):
+        paths = map(lambda x: self.vmpath + "/" + x, args)
+        return transaction.set_permissions(*paths)
+
     #
     # Function to update xenstore /dom/*
     #
@@ -1692,6 +1699,15 @@ class XendDomainInfo:
         except RuntimeError, exn:
             raise XendError(str(exn))
 
+    def _setTarget(self, target):
+        assert self.domid is not None
+
+        try:
+            SetTarget(self.domid, target)
+            self.storeDom('target', target)
+        except RuntimeError, exn:
+            raise XendError(str(exn))
+
 
     def _initDomain(self):
         log.debug('XendDomainInfo.initDomain: %s %s',
@@ -1756,6 +1772,8 @@ class XendDomainInfo:
                 self.native_protocol = channel_details['native_protocol'];
 
             self._introduceDomain()
+            if self.info.target():
+                self._setTarget(self.info.target())
 
             self._createDevices()
 

tools/python/xen/xend/image.py

@@ -222,6 +222,7 @@ class ImageHandler:
             vncopts = ""
             if passwd:
                 self.vm.storeVm("vncpasswd", passwd)
+                self.vm.permissionsVm("vncpasswd", { 'dom': self.vm.getDomid(), 'read': True } )
                 vncopts = vncopts + ",password"
                 log.debug("Stored a VNC password for vfb access")
             else:
@@ -280,6 +281,9 @@ class ImageHandler:
             env['XAUTHORITY'] = self.xauthority
         if self.vncconsole:
             args = args + ([ "-vncviewer" ])
+        xstransact.Mkdir("/local/domain/0/device-model/%i" % self.vm.getDomid())
+        xstransact.SetPermissions("/local/domain/0/device-model/%i" % self.vm.getDomid(),
+                        { 'dom': self.vm.getDomid(), 'read': True, 'write': True })
         log.info("spawning device models: %s %s", self.device_model, args)
         # keep track of pid and spawned options to kill it later
         self.pid = os.spawnve(os.P_NOWAIT, self.device_model, args, env)
@@ -422,7 +426,9 @@ class HVMImageHandler(ImageHandler):
         self.vm.storeVm(("image/dmargs", " ".join(self.dmargs)),
                         ("image/device-model", self.device_model),
                         ("image/display", self.display))
+        self.vm.permissionsVm("image/dmargs", { 'dom': self.vm.getDomid(), 'read': True } )
         self.vm.storeVm(("rtc/timeoffset", rtc_timeoffset))
+        self.vm.permissionsVm("rtc/timeoffset", { 'dom': self.vm.getDomid(), 'read': True } )
 
         self.apic = int(vmConfig['platform'].get('apic', 0))
         self.acpi = int(vmConfig['platform'].get('acpi', 0))

tools/python/xen/xend/xenstore/xsutil.py

@@ -22,6 +22,9 @@ def xshandle():
 def IntroduceDomain(domid, page, port):
     return xshandle().introduce_domain(domid, page, port)
 
+def SetTarget(domid, target):
+    return xshandle().set_target(domid, target)
+
 def GetDomainPath(domid):
     return xshandle().get_domain_path(domid)